Control system having a magnetic switch latching arrangement



Jan. 18, 1966 G. R. CHAFEE, JR 3,229,331

CONTROL SYSTEM HAVING A MAGNETIC SWITCH LATCHING ARRANGEMENT 3 Sheets-Sheet 2 Filed Sept. 11, 1963 F'IGZ.

INVENTOR.

G ENN R. HAFEE. 3R. Q) H\s ATTORNEY Jan. 18, 1966 e. R. CHAFEE, JR

CONTROL SYSTEM HAVING A MAGNETIC SWITCH LATCHING ARRANGEMENT 3 Sheets-Sheet 5 Filed Sept. 11, 1965 was \H5 ATTORNEY W7 8 NF s WA m w .W 6 R 9 N W 5 Q m m 1 re 8 e SULAQ m e 8 r 4 3 I00 I. 7 m

a A E Z 8 0.0 8 9 w ,0 A My 4 5 e 9 1% AM? .7 a w 7 A a United States Patent O 3,229,381 CONTROL SYSTEM HAVING A MAGNETIC SWITCH LATGHNG ARRANGEMENT Glenn R. Chafee, In, Louisville, Ky., assignor to General Electric Company, a corporation of New York Filed Sept. 11, 1963, Ser. No. 308,283 11 Claims. (Cl. 34-45) This invention relates to control systems, and more particularly to an improved arrangement for retaining, or latching, a magnetically operated switch in a predetermined position in response to a brief impulse. In its specific form, the invention relates to a control system for use in appliances such as dryers, wherein a magnetic switch controlling a device such as a relay is so arranged in the circuit that it may be latched into either its open or its closed position in response to a very brief magnetic impulse.

To an increasing extent, there are being used, in appliances such as clothes dryers, control devices which utilize the charging and discharging of a capacitor to initiate or terminate a function. For instance, a capacitor may be charged up to a level predetermined by the characteristics of a glow lamp (or some other type of electrical switch) in parallel with it, and may then discharge through a circuit including the glow lamp when the voltage across the capacitor becomes sufiiciently high to make the glow lamp conductive. There will, generally, be a circuit arranged for control by the glow lamp, for controlling the energization and de-energization of a device such as a heater control relay.

One problem that has been encountered in arrangements of this type is that, generally, the period of time which elapses before the capacitor is discharged to the point where the glow lamp is no longer conductive is very brief. In other Words, the structure controlled by the glow lamp is energized for only a very brief instant. This has heretofore required the provision of a device, usually a relay, capable of exceeding rapid response, and consequently quite expensive compared to the cost of the more conventional relays which are in substantial commercial use.

Accordingly, it is an object of this invention to provide, in a structure of the type described, an arrangement by which a conventional relay (or some other similar structure) may be made to respond to very brief electrical impulses.

A further more specific object of my invention is to achieve this goal by use of a magnetically responsive switch, i.e., a switch of the type which is actuated by magnetization of its parts.

Yet a more specific object of my invention is to achieve the control arrangement utilizing a reed switch, which is a magnetic switch of the type having two flexible contact arms of magnetic material biased away from each other; such switches are available at relatively low cost.

Another specific object of my invention is to achieve control of a magnetic switch by the inclusion in the control system of a small permanent magnet which provides a magnetic field about the switch tending to move it from its normal position to its other position. The field provided by the magnet is strong enough to hold the switch in its other position, but not strong enough to "ice move it thereto without help. There-fore, additional means may be provided in order to increase the field strength above that provided by the magnet so as to provide positive movement from the normal biased position of the switch to its other position, and to decrease the strength of the magnetic field so as to prevent the permanent magnet from retaining the switch in its other position.

Yet another specific object of my invention is to achieve the variation in the magnetic field provided by the magnet, at the end of a drying cycle in a dryer of the type described, by providing an electromagnetic coil in series with the glow lamp so that when the coil is energized it modifies the strength of the magnetic field to achieve the desired change in the position of the magnetic switch.

Yet another specific object of my invention is to achieve the cooperative relationship of the coil and mag net by causing the coil to be energized by direct current with a first polarity upon starting of the cycle so as to cause the switch to move to a first position by a first modification of the magnetic field, and by providing an electromagnetic impulse of the opposite polarity by passage of direct current through the coil in the opposite direction at the end of a dry-ing operation so as to provide the opposite modification of the magnetic field and the opposite movement of the switch.

A further specific object of the invention is the achievement of the initial affecting of the magnetic field pro vided by the permanent magnet about the switch by making the magnet movable automatically in response to the starting of the drying cycle.

In one aspect of my invention, I provide a control system for achieveing a predetermined condition in the treatment of articles; this may, for instance (and most typically) be a clothes dryer control system for achieving clothes dryness and shutting 01f the machine after the clothes have been sensed to be dry. Functional means ior changing the condition of the articles toward the predetermined condition is provided; in the case of a dryer, this will of course usually be in the form of heating means.

The operation of the functional means is controlled by a switch which has at least one member of magnetic material movable to open and closed positions. Generally this will be a normally open reed switch. A permanent magnet is formed and positioned so as to provide a magnetic field tending to keep the switch in the position other than that to which it is normally biased. In the case of a normally open reed switch this other position would be the closed position, of course. The magnetic field provided by the permanent magnet is strong enough so that it will keep the switch in this other position, but is not strong enough to move it to that position.

Suitable means are provided to affect the magnetic field in a first direction to provide a first position of the switch effective to start operation of the control system. In the various contemplated arrangements of my invention, this may either be a first D.C. circuit, with a coil being energized in a predetermined direction so as to provide an electromagnetic modification of the magnetic field; alternatively, it may simply be possible to move the permanent magnetby means of a pushbutton for instanceso that it either moves toward or away from the switch and thereby its effect is changed.

When the predetermined condition is sensed by the system, the coil (which is provided regardless of the means of initiating operation) is briefly energized with a polarity effective to change the magnetic field oppositely to the way it was changed at the beginning of the operation; this moves the switch to its other position. Since the initial effect was to start to move the switch to the position effective to start the operation, the effect of the momentary energization of the coil is the opposite, i.e., to terminate the operation.

With this structure, then, it is insured that the switch will be in a first position at the beginning of an operation (generally the closed position) and it is equally insured that the switch will move to its other position and will remain there at the end of the operation until such time as it is deliberately moved to its first position again.

The subject matter which I regard as my invention is particularly pointed out and distinctly claimed in the concluding portion of this specification. My invention, however, both as to organization and method of operation together with further objects and advantages thereof, may best be understood by reference to the following description taken in conjunction with the accompanying drawings.

In the drawings, FIGURE 1 is a side elevational view of a clothes dryer incorporating my improved control arrangement, the view being partly broken away and partly sectionalized in order to illustrate details;

FIGURE 2 is a horizontal sectional view of the dryer of FIGURE 1, with certain surfaces broken away and partly sectionalized to illustrate further details;

FIGURE 3 is a simplified schematic illustration of my improved control system as used in the control of the clothes dryer of FIGURES l and 2;

FIGURE 4 is a second embodiment of my invention as it may be applied to the clothes dryer of FIGURES 1 and 2; and

FIGURE 5 is a third embodiment of my invention as it may be applied to the clothes dryer of FIGURES 1 and 2.

Referring now to FIGURES 1 and 2, I have shown therein a domestic clothes dryer 1 including a clothes tumbling container or drum 2 provided with a suitable outer casing or cabinet 3 which completely encloses the drum on all sides. The drum is mounted for rotation within cabinet 3 on a substantially horizontal axis and is generally cylindrical in shape, having a first cylindrical outer wall portion 4, second and third cylindrical outer wall portions 5 and 6 located respectively adjacent the ends of the drum, a back wall 7, and a front wall 8.

-Outer wall portions 4, 5 and 6 are imperforate over their entire length so that the entire outer shell of the basket is imperforate. On the interior surface of central portion 4 there is provided a plurality of clothes tumbling ribs 9 formed of a suitable heat resistant insulating material such as general purpose phenolic resin. Over each rib extend a number of conductors or wires 10 and 11 which alternate with each other along the length of the rib. The purpose of these wires, and the structure to which they are related, will be more fully discussed herebelow.

The front of drum 2 is rotatably supported within the outer casing 3 by means of a pair of idler roller wheels 12 and 13 which are rotatably secured to the top of an upwardly extending member 14 secured at its base to the bottom 15 of the machine (FIGURE 1). Rollers 12 and 13 are disposed beneath the drum in contact with portion 6 thereof. The rear end of the drum receives its support from the roller wheel 15 which is positioned beneath portion 5 of the drum in supporting and frictionally driving engagement therewith.

from a belt 19 in turn powered by a pulley 20 mounted on the end of shaft 21 of an induction-type electric motor 22. The motor, pulleys, and roller 15 are so proportioned to drum 2 and to each other that drum 2 is rotated by roller 15 at the appropriate speed to provide tumbling action for articles of clothes and other fabrics placed therein.

In order that a stream of drying air be introduced into and passed through the clothes drum, the drum is provided with a central aperture 23 in its front wall 8 and with a plurality of perforations 24 extending in an annulus around the back wall 7. Rigidly secured to the rear wall 25 of casing 3 by any desired means, such as Welding at suitable points 26, for instance, is a bafiie member 27 which has secured thereto heating means such as an electric heater 28 appropriately insulated from the baffle member.

Heating elements 28 constitute functional means for changing the condition of the clothes toward the desired condition, i.e., dryness. They may be annular in shape so as to be generally coextensive with perforations 24 in drum 2. A baffle member 29 is rigidly secured to back wall 7 of the drum outside the ring of perforations 24 and within the stationary bafiie 27, so that an annular air inlet 30 is in effect formed by bafiies 27 and 29. Bafiie 29 is further provided with an annular series of openings 31. In this manner, a passage is formed .for air to enter annular openig 30 between the baffles, pass over the heating elements 28, and through openings 31 and perforations 24 into the interior :of drum 2.

In addition to their air guiding function, baffles 27 and 29 help rollers 12, 13 and 15 to support drum 2. Secured to the central portion 32 of bafiie 29 is a bracket 33 to which, in turn, is secured a stub shaft member 34 substantially coaxially positioned relative to drum 2. The central portion of bafiie 27 has a slot-like opening 36 formed therein. The slot is suitably formed (as more fully described in Patent 3,009,259 issued on November 21, 1961 to William F. Simpson and assigned to the same assignee as this invention) so as to permit stub shaft 34 a limited amount of movement in the vertical direction but virtually no movement in the horizontal direction. Thus, the slight vertical motions of the drum which result from the tumbling of the clothes can be accommodated, while at the same time undesirable horizontal motion is affirmatively prevented by engagement of stub shaft 34 and slot 36.

It is to be noted at this point that the stub shaft 34 is provided with a central opening 37. Wires 10 and 11 extend from ribs 9 around the back of the drum 2 and down through suitable openings in the baffle 29; the wires then extend through the opening 37 formed extending through the shaft 34. At the outer end of shaft 34 a disk 38 may be formed, as shown, with the conductors 10 being secured to a conductive outer ring portion 39 and the conductors 11 being secured to a conductive inner portion 40. Portions 39 and 40 are electrically insulated from each other; this may readily be done by making disk 38 of an insulating material, with the ring portions embedded therein. A contact member 41 is continuously in contact with the conductor portion 39, while similarly a conductor member 42 is continuously in contact with conductor portion 40 of the disk. Thus, all of the conductors 10 are connected to a stationary conductor 41, while all of the conductors 11 are similarly connected through similar means to a stationary conductor 42.

Front opening 23 of the drum is substantially closed by means of a stationary bulkhead generally indicated by the numeral 43. Bulkhead 43 is made up of a number of adjacent members including the inner surface 44 of an access door 45 mounted on the dryer cabinet, stationary frame 46 for the door, the inner surface 47 of an exhaust duct 48, and an annular flange 49 mounted on frame 46 and on the duct wall. It will be noted that a suitable clearance is provided between the inner edge of the drum opening 23 and the edge of bulkhead 43 so that there is no rubbing between the drum and the bulkhead during rotation of the drum. In order to prevent any substantial air leakage through opening 23 between the interior and the exterior of the drum a suitable ring seal 50, preferably formed of felt-like material, is secured to flange 49 in sealing relationship with the exterior surface of drum wall 8.

Front opening 23, in addition to serving as part of the air flow path through the drum, also serves as a means whereby clothes may be loaded into and unloaded from the drum. Door 45, whose inner surface forms part of the bulkhead closing the opening, is mounted on cabinet 3. When the door is opened, clothes may be placed into or removed from the drum through the door frame 46. It will be noted that the door includes an outer fiat imperforate section 51 and an inwardly extending hollow section 52 mounted on the flat outer section. Hollow section 52 extends into the door frame 46 when the door is closed, and the door surface 44 which comprises part of combination bulkhead 43 is actually the inner wall of the hollow section.

The air outlet from the basket is provided by a perforated opening 53 formed in the inner wall 44 of door section 52. The bottom wall section of door 52 and the adjacent wall of the door frame 46 are provided with aligned openings 54 and 55, opening 55 providing the entrance to duct 43. As shown, a lint trap 56, which may comprise a fine mesh bag, is preferably positioned in exhaust duct 48 at opening 55, the bag being supported by the door frame. Duct 48 leads to suitable air moving means which may, as shown, comprise a centrifugal blower 57 mounted on the shaft of motor 22 and thus driven directly by the motor. The outlet of blower 57 communicates with an outlet duct 58 (FIGURE 2) which extends through an opening 59 in the back 25 of cabinet 3.

The operation of dryer 1 is controlled by a new and improved control system as shown in the circuit diagram of FIGURE 3. As shown there, the entire control system of the machine may be energized across a three-wire power supply system which includes supply conductors 60 and 61 and a neutral conductor 62. For domestic use, conductors 60 and 61 will normally be connected across a 220 volt power supply, with 110 volts appearing between the neutral line 62 and each of the conductors and with the neutral line being at ground voltage.

Motor 22 is connected between conductors 60 and 62. The motor includes, in the usual manner, a main winding 63 and a start winding 64 both connected at a common end to a conductor 65 which, through a conventional door switch 66 (which is closed when door 45 is closed and is opened when the door is open), connects conductor 65 to supply conductor 62.

The start winding 64 is connected in parallel with main winding 63 through a switch 67 controlled by a speed responsive device such as that shown at 68. Speed responsive device 68 is schematically shown as connected to rotor 69 of the motor. Switch 67 is engageable with either of contacts 79 or 71, being engaged with contact 70 when the machine is at rest and moving into engagement with contact 71 as the motor comes up to speed. It can readily be seen that engagement with contact 79 connects the start winding 64 in parallel with main winding 63, while movement of switch 67 away from this position opens the start winding. Thus, as rotor 69 comes up to speed the start winding becomes de-energized and the motor then continues to run on main winding 63 alone.

The starting of the motor is provided by a manually operable pushbutton switch 72 which connects the motor to supply conductor 60. This switch, which is normally biased to an open position, may be pushed closed by manual pressure so that energization of the motor is provided. Within less than a second, under normal circumstances, the motor comes up to speed so that switch 67 engages contact 71.

The depression of pushbutton switch 72 also completes a direct current energizing circuit through a coil 73 as follows: starting at conductor 60, the circuit extends through switch 72, switch 67, contact 71 (after the motor has come up to speed), a thermostatic switch 74 (shown as a bimetallic element) which is normally in engagement with a contact 75, and a conductor 76 to a switch 77 controlled by a main relay 78. Switch 77 is engageable with a contact 79 when the relay is de-energized and with a contact 80 when the relay is energized. From contact 79, the circuit then continues through a conductor 81, which includes a conventional rectifying device 82, such as a diode, and then through coil 73 to conductor 62. Coil 73 is in controlling relationship to a switch 84 which is of the type having at least one member movable in response to a magnetic field. Preferably, and as shown, switch 84 is a reed switch wherein both arms are of magnetic material and are biased to an open position, i.e., away from each other.

As an important aspect of my invention, I provide a small permanent magnet 85. Magnet 85 is so positioned relative to switch 84, and is of such a size, that when the contact arms of switch 84 are in their normally biased opened position the magnetic field provided by magnet 85 is not suificient to cause them to close even though the field tends to make the arms attract each other. However, when the contact arms have already been moved together, that is, the switch has been closed, the magnetic field provided by magnet 85 is sufiiciently strong to retain the contact arms in that position. This is a relationship well known to those skilled in the art: the magnetic field strength required to retain parts in a given position is substantially less than that required to move them to that position from a dilferent position.

Coil 73, when energized by direct current with a first polarity, provides an electromagnetic field which is additive to the field provided by magnet 85, and results in the closing of switch 84. Direct current energization of coil 73 with the opposite polarity has the opposite eifect on the magnetic field. In other words, the electromagnetic field provided by coil 73 when energized with the second polarity subtracts from the magnetic field of magnet 85. As a result, if magnet 85 has been holding switch 84 closed, the energization of coil 73 with a second polarity decreases the magnetic field to the point that the arms of the reed switch are no longer held together, and move apart under their own spring bias, that is, they open.

Reed switches such as switch 84 have an exceedingly fast response, on the order of 1 millisecond or less. Thus, a momentary energization of coil 73 is sufiicient to provide for the opening or closing of the reed switch.

In essence then, the direction, or polarity, of current through coil 73, as determined by rectifier 82 in the energizing circuit described, is such as to provide an electromagnetic field additive to that of magnet 85, and effect a closing force on the reed switch 8-4. In other words, if the switch was previously open, it will be closed as a result of the passage of direct current through coil 73. The closure of switch 84 causes energization of relay 78 (switch 72 still being closed), which then closes relay contact 86 and moves relay contact 77 over into engagement with contact 80.

The movement of switch 67 into engagement with contact 71, in addition to disconnecting start winding 64, provides for continued energization of run winding 63 of the motor independently of push-button start switch 72 as follows: starting at conductor 60, the circuit extends through contact 80 and relay switch 77, conductor 76, contact 75 and thermostatic switch 74, contact 71, switch 67, and then through the main winding 63 and switch 66 to neutral conductor 62. Thus, the motor continues to run after switch 72 is opened. When enough heat is supplied to switch 74 to make it move up into engagement with a contact 87, the energizing circuit for motor winding 63 is completed independently of relay switch 77.

An energizing circuit for relay 78 is also completed independently of switch 72 as follows: starting at conductor 69, the circuit extends as described in connection with the motor to switch 67; then from contact 71 the circuit proceeds through the main relay 78 and switch 84 to conductor 62. Thus, as long as switch 84 remains closed the relay 78 remains energized. The relay energization completes a circuit for heater 28- from conductor 60 through contact 80 and relay switch 77, then through the heater 28 itself, through any desired and appropriate thermostatic control 88 for controlling the energization of the heater in the conventional manner, and through relay contact 86 to conductor 61. In this manner, the heater 28 is energized across the full 220 volt potential.

In order to control the length of the drying operation, a direct current circuit is provided which includes a second rectifier 89. From rectifier 89, the circuit proceeds through a resistor 90 of substantial magnitude, as high as is practical for the environment and use to which it is to be put. A value of 15 to 30 megohms is appropriate for this purpose, for instance. In series with resistor 90 is a capacitor 91, and it will readily be seen that under normal circumstances capacitor 91 and resistor 90 form together an RC time relay constant circuit, with the length of the time delay (in seconds) being dependent in the usual manner on the product of the resistance in ohms multiplied by the capacitance in farads. Since, a fairly high time constant is desirable, a capacitor 91 of reasonably large capacitance is desirable.

Connected across the capacitor is a voltage sensitive device 92, that is, a device which becomes conductive only when a predetermined voltage is put across it. This function may readily be carried out by a relatively inexpensive glow tube such as, for instance, that marketed by the General Electric Company as Model No. NE-Z. Included in series with glow tube 92 and in parallel with capacitor 91 is the coil 73 controlling switch 84.

As long as capacitor 91 is not charged up to the firing voltage of glow tube 92, there will be no current passing through coil 73 during operation of the machine, and therefore switch 84 will remain closed. However, when the capacitor does become sufficiently charged, glow tube 92 will fire and remain conductive during the brief period of time that it takes to discharge the capacitor to the point where there is insufiicient potential to keep the glow tube conductive. During this period of time coil 73 is energized with a polarity opposite to that which was provided during its energization at the beginning of the cycle. As a result, the electromagnetic field, instead of adding to the magnetic field of magnet 85, subtracts therefrom. This decreases the total magnetic field to a point where reed switch 84 is no longer held closed by magnet 85, but instead is permitted to move to its ordinary open position. When coil 73 is de-energized, switch 84 stays open because the magnetic field of magnet 85 alone is not strong enough to close it. Relay 78 is therefore de-energized to disconnect heater 28 and terminate the heat drying operation.

At this point, in a normal drying cycle, thermostat 74 (which is positioned to sense clothes temperature, as shown in FIGURE 1) will have moved into engagement with contact 87. Motor 22 will therefore continue to operate to provide a cool-down, during which the clothes are tumbled without heat. When the clothes have cooled down sufficiently, the thermostatic switch 74 will sense this and will return into engagement with contact 75 thereby opening all circuits and terminating operation of the machine.

The moment at which glow tube 92 permits energization of coil 73 is controlled by the conductors 10 and 11 which, as shown schematically in FIGURE 3, are also connected across capacitor 91. This means that as long as clothes are wet and are forming a low resistance bridge between the sensing fingers, or conductors, 10 and 11, there is essentially a short circuit across the capacitor and no charging will occur. As the clothes become dry, there starts to be an appreciable resistance between fingers 10 and 11 so that charging of the capacitor starts to occur,

with the charging bemg subject to the characteristics of the RC circuit. Thus, capacitor 91 will not even start to charge while there is a substantial amount of moisture in the clothes. It is only as the clothes start to become dry that charging of the capacitor starts.

In effect what is achieved by the RC time constant circuit provided by resistor 90 and capacitor 91 is a predetermined additional period of time after the clothes have started to dry during which further heat drying is provided. This is important since the resistance between fingers 10 and 11 becomes quite high before the clothes are truly dry to the touch, that is, while the clothes still have a moisture retention on the order of 15% to 25%. Thus, the time constant provided by resistor 90 and capacitor 91 gives an additional period of time after this state is reached during which suflicient additional heat may be provided to the clothes to cause them to be fully dry to the touch.

The operation of the circuit will now be briefly set forth. As described, when switch 72 is depressed, motor 22 is started and then continues operation through the centrifugal switch 67. Also, the heater starts operation as a result of the energization of relay 78 and the closing of relay contacts 77 and 86. Also, as an important aspect of my invention, reed switch 84, which is initially in its normal open position notwithstanding the magnetic field of magnet because of the normal bias of the switch to open position (and because the last impulse from coil 73 was to cause the switch to open), is closed through the circuit previously described. Thus, the machine starts in operation, with the charging of capacitor 91 being prevented by the high conductivity of the wet clothes across conductors 10 and 11. When the temperature of the clothes starts to rise, thermostat 74 trips up into engagement with contact 87, but as previously explained this makes no immediate difference in the operation of the machine. It does, however, make the continued operation of motor 22 independent of relay switch 77.

As the clothes start to approach dryness, a substantial resistance starts to exist between fingers 10 and 11 and this permits capacitor 91 to start charging. After a time period which, in the illustrated circuit, is determined by the RC time constant of resistor 90, capacitor 91, and the clothes resistance, the capacitor is charged sufliciently to fire glow tube 92 and cause passage of current through coil 73 in a direction opposite to that which caused switch 84 to close at the beginning of the operation. This opposite direction of energization of coil 73 has the opposite eflect on the magnetic field of magnet 85 from before, that is, instead of strengthening the magnetic field it substantially weakens the magnetic field. Without the magnetic field of magnet 85 holding switch 84 in a closed position, the switch moves to its normally open position and then remains there, even when the coil is de-energized. This continued open condition of switch 84 de-energizes relay 78 and the relay contacts move back to the position shown. In this position, the heater 28 is de-energized. However, because of the tripped condition of thermostat 74 a circuit is still completed for the energization of motor 22, and the motor continues to run until the clothes have cooled down to the point where thermostat 74 trips back into engagement with contact 75 thereby de-energizing all components of the machine.

There are several advantages resulting from the latching characteristics of the circuit set forth above. If the drying cycle should be temporarily stopped, as for instance by opening the door and thereby opening door switch 66, after thermostat 74 has tripped into engagement with contact 87, then, when the machine is restarted, there will not be another pulse provided to coil 73. As a result, the cycle is restarted with the sensing elements in essentially the same condition.

A further advantage results because the pulse provided through coil 73 and capacitor 91 is of an opposite polarity to the charging of the capacitor during operation of the 9 machine. As a result, any residual charge which may well be stored in the capacitor from a previous cycle is wiped out. This is important because, with the normal characteristics of a glow tube such as the one shown at 92, it stops conducting while there is still an appreciable amount of voltage across the capacitor.

To phrase it differently, with the applicants structure the reverse polarity impulse at the beginning of a cycle prevents a residual capacitor voltage from existing, which would short-en substantially the time elapsed, once the capacitor started charging, before the glow tube firing voltage was reached. This is important when dry clothes are inserted into the machine as is sometimes done to flufi them, or dewrinkle them. With my structure the glow tube 92 will fire when the initial impulse is applied to start a cycle, and the capacitor will, in fact, be charged negatively, so that before the end of such a cycle occurs the voltage across the capacitor passes from negative to positive in order to fire the glow tube again and cause termination of the cycle.

Also, there is the very important advantage that the drop-out time of the main relay 78 becomes unimportant, with reed switch 84 being used for a latching relay with the help of magnet 85 and coil 73. This permits use of a far more economical relay.

Referring now to FIGURE 4, there is shown another embodiment of my invention wherein like numerals are used for parts which are the same as those shown in FIGURE 3. Except for the particular difference in the inventive aspect relating to the latching relay, the circuit of FIGURE 4 is substantially similar to that of FIGURE 3 with the single exception that thermostat 74- of FIG- URE 3, which was provided to permit cool-down, and the circuitry associated therewith, have been eliminated in order to simplify and clarify the circuit of FIGURE 4.

The same basic concept is used of causing magnet 85 to control reed switch 84 in cooperation with coil 73 so that a latching effect is obtained in the condition of the switch 84, and again this is done by providing pulses of opposite polarity through coil 73 in order to open and close switch 84. However, where the circuit of FIG- URE 3 provided a rectifier in each of the direct current circuits for permitting direct current of opposite polarities to be provided to coil 73, the opposite polarity is achieved in the embodiment of FIGURE 4 by the single rectifier 89 in cooperation with a switch 93.

The normal position of switch 93 is, as shown, in engagement with contact 94. However, when button 72 is depressed switch arm 93 is moved into engagement with contact 95. When button 72 is depressed, and motor 22 has come up to speed sufficiently for arm 67 to engage contact 71, a circuit is provided as follows: from conductor 60, the circuit extends through switch 72, switch arm 67, contact 71, rectifier 89, conductor 95, switch 93, coil 73, glow lamp 92, and conductors 11 and to conductor 62, it being understood that a load of wet clothes is positioned within the machine and is bridging conductors 10 and 11. This then provides a pulse of a predetermined polarity to coil 73, and the coil accordingly assists magnet 85 in closing switch 84.

Once the relay closes, then the circuit for coil 73 is as follows: starting at switch 60, the circuit proceeds through contact 80, closed relay switch 77, switch 67, contact 71, rectifier 89, resistor 90, glow lamp 92, coil 73, switch 93 and contact 94 to conductor 62. The capacitor 91 and conductors 10 and 11 are connected in parallel with glow lamp 92 and coil 73 as explained previously in connection with FIGURE 3. It will readily be seen that the movement of switch 93 back to the position in which it is biased, in engagement with contact 94, will, when glow lamp 92 becomes conductive, provide a pulse of opposite polarity to coil 73 Causing the electromagnetic field of the coil to oppose the field of magnet 85, permitting switch 84 to open and deenergize relay 78 as previously explained.

Other than the manner of providing the pulses of opposite polarity for coil 73, the operation of the circuit of FIGURE 4 is essentially the same as that of FIGURE 3 and therefore will not be described in detail, it being understood that the pulse provided to the coil is such as to cause switch 84 to close when start button 72 is depressed, and to cause it to open when the capacitor becomes charged during the drying of clothes to the point where the glow lamp 92 fires.

The circuit of FIGURE 4 has been described with the assumption that the gap between conductors 10 and 11 will be bridged by wet clothes when pushbutton 72 is operated, in order for the circuit to be completed to provide the appropriate pulse to coil 72. However, it is of course possible that an operator may insert dry clothes into the machine. For instance, this will occur where the clothes are merely to be fluffed, an operation which is quite often provided on commercially sold drying machines; the circuitry for this operation is not shown in the present case because it has no application to the present invention and would merely complicate the disclosure.

Where dry clothes are put in the dryer, it is easily possible to insure, in the circuit of FIGURE 4, that the desired initial pulse will be provided to coil 73 by providing, in parallel with conductors 10 and 11, a resistor 96. Resistor 96 may, for instance, be on the order of 100,000 ohms, in series with a switch 97 also is controlled by button 72. Switch 97 is normally open, but closes during depression of button 72 so as to insure the completion of a circuit regardless whether wet clothes are bridging the conductors 10 and 11 or not.

It will be understood that the advantages obtained from the circuit of FIGURE 4 are basically the same as those enumerated in connection with the arrangement of FIG- URE 3.

Referring now to FIGURE 5, there is shown a third embodiment of my invention wherein like numerals are used for parts which are the same as those shown in FIG- URE 3. The circuit of FIGURE 5 is identical to that of the embodiment shown in FIGURE 3 except for the elimination of contact 79, conductor 81 and rectifier 82; it will be understood, therefore, that except for the circuit for energizing coil 73 with a first polarity so as to add to the magnetic held of magnet 35, the operation of the entire circuit is identical to that of FIGURE 3.

In the embodiment of FIGURE 5, instead of using energization of coil 73 to increase the magnetic field and close switch 84, magnet is movably mounted. In response to depression of pushbutton '72, the magnet is physically moved closer to reed switch 84. Of course, the closer magnet 85 is to switch 84 the stronger the magnetic field affecting the contact arms of switch 84. As a result, movement of magnet 85 to a position adjacent the reed switch 84 causes the contact arms of the reed switch to close. When pushbutton 72 is released, and magnet 35 moves back to its ordinary position, the reed switch contact arms will remain closed for the reasons set forth in connection with the first embodiment, that is, the magnetic field of magnet 85 is still strong enough to keep the arms of switch 84 closed even though it is not strong enough to cause them to close. Thus, the initiation of an operation is obtained, as before, by depressing button 72, but this time, in the arrangement of FIGURE 5, the depression of button 72 is effective itself to increase the strength of the magnetic field by the physical movement of magnet 85.

The remainder of the operation of the circuit is identical to that of the circuit of FIGURE 3. At the end of an operation the glow tube 92 is fired by the discharge of capacitor 91, energizing coil 73 with a polarity causing its electromagnetic field to oppose the field of magnet 85 and permit switch 84 to open.

While in accordance with the patent statutes I have described what at present are considered to be the preferred embodiments of my invention, it will be obvious to those skilled in the art that various changes and modifications may be made therein without departing from the invention. It is therefore intended in the appended claims to cover all such equivalent variations which wall within the true spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. A control system for achieving a predetermined condition in the treatment of articles comprising:

(a) functional means for changing the condition of the articles toward the predetermined condition;

(b) a switch having at least one member of magnetic material movable to first and second positions and biased to its first position, said switch being arranged to cause operation of said functional means in said second position and preclude operation of said functional means in said first position;

(c) a permanent magnet formed and positioned to provide a magnetic field effective by itself to keep said switch in said second position once it has been moved there but not effective by itself to move said switch from its first position;

((1) a coil;

(e) means for increasing the strength of the magnetic field provided to said switch sufiiciently to move said switch from its first position to its second position;

(f) a direct current circuit for energizing said coil with a polarity such as to provide an electromagnetic field opposing said magnetic field, said coil when energized in said circuit decreasing the magnetic field to the point where said switch returns to its first position;

(g) manually operable means for providing operation of said field strength increasing means thereby to move said switch to its second position and initiate operation of said functional means;

(h) and condition responsive means for momentarily completing said coil energizing circuit in response to substantial achievement of said predetermined condition thereby to return said switch to its first position.

2. A control system for achieving a predetermined condition in the treatment of articles comprising:

(a) functional means for changing the condition of the articles toward the predetermined condition;

(b) a switch having at least one member of magnetic material movable to first and second positions and biased to its first position, said switch being arranged to cause operation of said functional means in said second position and preclude operation of said functional means in said first position;

(c) a permanent magnet formed and positioned to provide a magnetic field effective by itself to keep said switch in said second position once it has been moved there but not effective by itself to move said switch from its first position;

(d) a coil;

(e) first and second direct current circuits for energizing said coil with opposite polarities, said coil when energized in said first circuit providing an electromagnetic field additive to said magnetic field sufficiently to cause movement of said switch from said first position to said second position, said coil when energized in said second circuit providing an electromagnetic field opposing said magnetic field sufliciently to permit movement of said switch back to its first position;

(f) manually operable means for momentarily completing said first circuit to initiate operation of said functional means;

(g) and condition responsive means for momentarily completing said second circuit in response to substantial achievement of said predetermined condition thereby to return said switch to its first position.

3. A control system for achieving a predetermined condition in the treatment of articles comprising:

(a) functional means for changing the condition of the articles toward the predetermined condition; (b) a relay including contacts positioned in an open position and movable to a closed position upon energization of said relay, said contacts being arranged to control operation of said functional means;

(0) magnetic switch means including at least one member of magnetic material movable to open and closed positions and biased to its open position, said magnetic switch means being arranged in series with said relay to control energization thereof;

(d) a permanent magnet formed and positioned to provide a magnetic field about said switch means of sufficient strength to keep said switch means in its closed position once it has been moved there but not effective by itself to move said switch means from its open position to its closed position;

(e) a coil;

(f) first and second direct current circuits for energizing said control with opposite polarities, said coil when energized in said first circuit providing an electromagnetic field additive to said magnetic field sufiiciently to cause said magnetic switch means to close, said coil when energized in said second circuit providing an electromagnetic field opposing said magnetic field sufiiciently that said magnetic switch means moves to its normal open position;

(g) manually operable means for momentarily completing said first circuit to provide energization of said relay and consequent operation of said functional means;

(h) and condition responsive means for momentarily completing said second circuit in response to substantial achievement of said predetermined condition thereby to return said switch means to its open position.

4. A control system for sensing the dryness of clothes in a clothes dryer comprising:

(a) means for drying the clothes including heating means;

(b) a relay controlling said heating means, said heating means being operable when said relay is energized and being shut off when said relay is de-energized;

(c) magnetic switch means including at least one member of magnetic material movable to open and closed positions and biased to its open position, said magnetic switch means being positioned in series with said relay to control energization thereof;

(d) a permanent magnet formed and positioned to provide a magnetic field about said switch means of sufi'icient strength to keep said switch mean-s in its closed position once it has been moved there but not effective by itself to move said switch means from its open position to its closed position;

(e) a coil;

(f) first and second direct current circuits for energizing said coil with opposite polarities, said coil when energized in said first circuit providing an electromagnetic field additive to said magnetic field sufficiently to cause said magnetic switch means to close, said coil when energized in said second circuit providing an electromagnetic field opposing said magnetic field sufiiciently that said magnetic switch means moves to its normal open position;

g) manually operable means for momentarily completing said first circuit to initiate operation of said heating means;

(h) and dryness responsive means for momentarily completing said second circuit in response to substantial achievement of dryness thereby to return said magnetic switch means to its open position.

5. The system defined in claim 4 wherein said dryness responsive means comprises a resistor, a capacitor in series with said resistor, and conductors positioned to be bridged by clothes connected in parallel with said capacitor and in series with said resistor, whereby a low resistance across said capacitor is provided when clothes are wet and the resistance across said capacitor rises as the clothes become dryer, said coil also being positioned in parallel with said capacitor and in series with said resistor; and voltage responsive means in series with said coil and in parallel with said capacitor, said voltage responsive means preventing passage of current through said coil until the voltage across said capacitor reaches a predetermined level at which time said voltage responsive means becomes conductive until the voltage across said capacitor falls below said predetermined level and thereby momentarily provides for passage of current through said coil.

6. A control system for terminating operation of a clothes dryer after the clothes therein achieve a predetermined dryness comprising:

(a) a means for drying clothes including heating means;

(b) a relay arranged to control operation of said heating means, said relay when energized providing for operation of said heating means and when de-energized preventing operation of said heating means;

(c) magnetic switch means including at least one member of magnetic material movable to open and closed positions and biased to its open position, said magnetic switch means being positioned in series with said relay to control energization thereof;

((1) a permanent magnet formed and positioned to provide a magnetic field about said switch means of sufiicient strength to keep said switch means in its closed position once it has been moved there but not effective by itself to move said switch means from its open position to its closed position;

(e) a coil;

(f) a first direct current circuit for energizing said coil with a first plurality including a manually operable switch, and a first rectifying device in series with each other and said coil;

(g) a second direct current circuit for energizing said coil with an opposite polarity to that of said first circuit including a second rectifying device half wave rectifier and dryness responsive means for momentariiy completing said second circuit in response to achievement of the predetermined condition of dryness;

(h) said coil when energized in said first circuit providing an electromagnetic field additive to said magnetic field sufficient to close said magnetic switch means and when energized in said second circuit providing an electromagnetic field opposing said magnetic field sufficiently to permit said magnetic switch means to open;

(i) and manual means for momentarily closing said manually operable switch thereby to complete said first circuit and initiate operation of said heating means by energization of said relay.

7. A control system for terminating operation of a clothes dryer after the clothes therein achieve a predetermined dryness comprising:

(a) means for drying clothes including heating means;

(b) a relay arranged to control operation of said heating means, said relay when energized providing for operation of said heating means and when de-energized preventing operation of said heating means;

(c) magnetic switch means including at least one member of magnetic material movable to open and closed positions and biased to its open position, said magnetic switch means being positioned in series with said relay to control energization thereof;

(d) a permanent magnet formed and positioned to provide a magnetic field about said switch means of suflicient strength to keep said switch means in its closed position once it has been moved there but not etfective by itself to move said switch means from its open position to its closed position;

(e) a coil;

(f) first and second direct current circuits for energizing said coil with opposite polarities, said coil when energized in said first circuit providing an electromagnetic field additive to said magnetic field sufficiently to close said magnetic switch means and when energized in said second circuit providing an electromagnetic field opposing said magnetic field sufficiently to permit said magnetic switch means to return to its open position;

(g) a rectifying device for providing direct current to both said first and second direct current circuits;

(h) a manually operable switch having first and second positions and biased to said first position, said manually operable switch in its first position enabling completion of said second circuit and in its second position providing completion of said first circuit whereby said magnetic switch means is closed to initiate a drying operation;

(i) and dryness responsive means for momentarily completing said second circuit in response to a predetermined condition of dryness when said manually operable switch is in its first position thereby to cause said magnetic switch means to return to its first position.

8. The system defined in claim 7 wherein said dryness responsive means comprises a resistor, a capacitor in series with said resistor, and conductors positioned to be bridged by clothes connected in parallel with said capacitor and in series with said resistor whereby a low resistance across said capacitor is provided when clothes are wet and the resistance across said capacitor rises as the clothes become dryer, said coil also being positioned in parallel with said capacitor and in series with said resistor; and voltage responsive means in series with said coil and in parallel with said capacitor, said voltage responsive means preventing passage of current through said coil until the voltage across said capacitor reaches a predetermined level at which time said voltage responsive means becomes conductive until the voltage across said capacitor falls below said predetermined level and thereby momentarily provides for passage of current through said coil.

9. The apparatus defined in claim 1 wherein said switch is a reed switch.

10. The apparatus defined in claim 8 wherein means for bypassing said conductors positioned to be bridged by clothes are provided, said bypassing means being arranged to be completed when said manually operable switch is movable to its second position.

11. A control system for achieving a predetermined condition in the treatment of articles comp-rising:

(a) functional means for changing the condition of the articles toward the predetermined condition;

(b) magnetic switch means including at least one member of magnetic material movable to open and closed positions and biased to its open position, said magnetic switch means being arranged to cause operation of said functional means when in its closed position and to preclude operation of said functional means when in its open position;

(c) a permanent magnet movably positioned and biased to a position wherein it provides a magnetic field effective to keep said switch means closed once it has been moved to the closed position but not effective by itself to move said switch means from its open position to its closed position;

((1) a coil;

(e) manually operable means for momentarily moving said magnet towards said switch means so as to increase the magnetic field about said switch means sufiiciently to close said switch and thereby initiate operation of said functional means;

(f) a direct current circuit for energizing said coil with a polarity such as to provide an electromagnetic field opposing said magnetic field sufficiently that when said coil is energized said switch means returns to its biased open position;

(g) and condition responsive means for momentarily completing said second circuit in response to sub- 16 stantial achievement of said predetermined condition thereby to decrease said magnetic field to the point where said switch means returns to its first position.

5 References Cited by the Examiner UNITED STATES PATENTS 3,042,107 7/1962 Burckhardt 158-28 3,180,038 4/1965 Chafiee 34-48 1O WILLIAM F. ODEA, Primary Examiner.

D. A. TAMBURRO, Assistant Examiner.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION 7 Patent No. 5,229,381 Januarx 18, 1966 Glenn R. Chafee, Jr.

It is hereby certified that error appears in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

Column 12, line 22, for "control" read coil,

Signed and sealed this 10th day of January 1967.

(SEAL) Amt:

ERNEST W. SWIDER EDWARD J. BRENNER mating Officer ner ofPatcnts 

1. A CONTROL SYSTEM FOR ACHIEVING A PREDETERMINED CONDITION IN THE TREATMENT OF ARTICLES COMPRISING : (A) FUNCTIONAL MEANS FOR CHANGING THE CONDITION OF THE ARTICLES TOWARD THE PREDETERMINED CONDITION; (B) A SWITCH HAVING AT LEAST ONE MEMBER OF MAGNETIC MATERIAL MOVABLE TO FIRST AND SECOND POSITIONS AND BIASED TO ITS FIRST POSITION, SAID SWITCH BEING ARRANGED TO CAUSE OPERATION OF SAID FUNCTIONAL MEANS IN SAID SECOND POSITION AND PRECLUDE OPERATION OF SAID FUNCTIONAL MEANS IN SAID FIRST POSITION; (C) A PERMANENT MAGNET FORMED AND POSITIONED TO PROVIDE A MAGNETIC FIELD EFFECTIVE BY ITSELF TO KEEP SAID SWITCH IN SAID SECOND POSITION ONCE IT HAS BEEN MOVED THERE BUT NOT EFFECTIVE BY ITSELF TO MOVE SAID SWITCH FROM ITS FIRST POSITION, (D) A COIL; (E) MEANS FOR INCREASING THE STRENGTH OF THE MAGNETIC FIELD PROVIDED TO SAID SWITCH SUFFICIENTLY TO MOVE SAID SWITCH FROM ITS FIRST POSITION TO ITS SECOND POSITION; (F) A DIRECT CURRENT CIRCUIT FOR ENERGIZING SAID COIL WITH A POLARITY SUCH AS TO PROVIDE AN ELECTROMAGNETIC FIELD OPPOSING SAID MAGNETIC FIELD, SAID COIL WHEN ENERGIZED IN SAID CIRCUIT DECREASING THE MAGNETIC FIELD TO THE POINT WHERE SAID SWITCH RETURNS TO ITS FIRST POSITION; (G) MANUALLY OPERABLE MEANS FOR PROVIDING OPERATION OF SAID FIELD STRENGTH INCREASING MEANS THEREBY TO MOVE SAID SWITCH TO ITS SECOND POSITION AND INITIATE OPERATION OF SAID FUNCTIONAL MEANS; (H) AND CONDITION RESPONSIVE MEANS FOR MOMENTARILY COMPLETING SAID COIL ENERGIZING CIRCUIT IN RESPONSE TO SUBSTANTIAL ACHIEVEMENT OF SAID PREDETERMINED CONDITION THEREBY TO RETURN SAID SWITCH TO ITS FIRST POSITION. 